The overall goal of the proposed research is to elucidate the molecular mechanisms responsible for glial cell differentiation and to exploit the signaling components involved in differentiation as tools for the ultimate treatment of low grade gliomas. Previous work by our group established that autocrine loop PDGF signaling causes a dedifferentiation of astrocytes to glial progenitors in culture, and formation of low-grade gliomas in mice. Pharmacologic blockade of PDGF receptor tyrosine kinase activity causes the cells to revert to differentiated astrocyte-like cells. We therefore hypothesize that agents that are known to promote differentiation will reverse the tumorigenic phenotype. Our studies in primary oligodendrocytes have identified key signaling proteins, including Fyn, 190RhoGAP, Rho, and Cdk inhibitors, that are involved in oligodendrocyte differentiation. We therefore intend to directly test the abilitiy of these signaling molecules to regulate glial cell differentiation in culture, and oligodendroglioma formation in mice and humans, as follows: Aim 1: To determine the role of Src family kinases, the Rho pathway, Cdk inhibitors and Rb family members in glial cell differentiation in culture. GFAP-PDGF as well as nestin-PDGF expressing cells will be infected with RCAS vectors encoding wt and mutant forms of Fyn, p190RhoGAP, Rho, p21 and p27 and the effects on growth and differentiation of the cells will be determined. Aim 2: To determine the role of Src family kinases, the Rho pathway, Cdk inhibitors and Rb family members in oligodendroglioma formation in vivo. Transgenic mice will be utilized to determine the role of the above molecules in tumor formation in mice. Aim 3: To analyze human oligodendrogliomas for activity of the above molecules and pathways in order to validate the proposed experimental models. The activity of the above proteins in human glioma tumor samples will be determined. Aim 4: To carry out clinical trials of inhibitors of PDGF, Rho and Rb family members in patients with oligodendrogliomas. We will test the ability of PTK787, an inhibitor of PDGF and VEGF receptors, and SAHA, an inhibitor of histone deacetylases, to block the activities of their respective targets in human gliomas using clinical trials in low-grade glioma patients.